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GNU C Library master sources branch release/2.26/master updated. glibc-2.26-207-gc165427
- From: stli at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 7 Feb 2019 14:50:56 -0000
- Subject: GNU C Library master sources branch release/2.26/master updated. glibc-2.26-207-gc165427
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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=c165427d55d4eefca2dd324073c52f54db0db15a
commit c165427d55d4eefca2dd324073c52f54db0db15a
Author: Stefan Liebler <stli@linux.ibm.com>
Date: Thu Feb 7 15:18:36 2019 +0100
Add compiler barriers around modifications of the robust mutex list for pthread_mutex_trylock. [BZ #24180]
While debugging a kernel warning, Thomas Gleixner, Sebastian Sewior and
Heiko Carstens found a bug in pthread_mutex_trylock due to misordered
instructions:
140: a5 1b 00 01 oill %r1,1
144: e5 48 a0 f0 00 00 mvghi 240(%r10),0 <--- THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
14a: e3 10 a0 e0 00 24 stg %r1,224(%r10) <--- last THREAD_SETMEM of ENQUEUE_MUTEX_PI
vs (with compiler barriers):
140: a5 1b 00 01 oill %r1,1
144: e3 10 a0 e0 00 24 stg %r1,224(%r10)
14a: e5 48 a0 f0 00 00 mvghi 240(%r10),0
Please have a look at the discussion:
"Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggerede"
(https://lore.kernel.org/lkml/20190202112006.GB3381@osiris/)
This patch is introducing the same compiler barriers and comments
for pthread_mutex_trylock as introduced for pthread_mutex_lock and
pthread_mutex_timedlock by commit 8f9450a0b7a9e78267e8ae1ab1000ebca08e473e
"Add compiler barriers around modifications of the robust mutex list."
ChangeLog:
[BZ #24180]
* nptl/pthread_mutex_trylock.c (__pthread_mutex_trylock):
Add compiler barriers and comments.
(cherry picked from commit 823624bdc47f1f80109c9c52dee7939b9386d708)
diff --git a/ChangeLog b/ChangeLog
index 6570bc6..b0afd11 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2019-02-07 Stefan Liebler <stli@linux.ibm.com>
+
+ [BZ #24180]
+ * nptl/pthread_mutex_trylock.c (__pthread_mutex_trylock):
+ Add compiler barriers and comments.
+
2019-02-04 H.J. Lu <hongjiu.lu@intel.com>
[BZ #24155]
diff --git a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c
index ec7da61..d478eca 100644
--- a/nptl/pthread_mutex_trylock.c
+++ b/nptl/pthread_mutex_trylock.c
@@ -92,6 +92,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
&mutex->__data.__list.__next);
+ /* We need to set op_pending before starting the operation. Also
+ see comments at ENQUEUE_MUTEX. */
+ __asm ("" ::: "memory");
oldval = mutex->__data.__lock;
do
@@ -117,7 +120,12 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
/* But it is inconsistent unless marked otherwise. */
mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
+ /* We must not enqueue the mutex before we have acquired it.
+ Also see comments at ENQUEUE_MUTEX. */
+ __asm ("" ::: "memory");
ENQUEUE_MUTEX (mutex);
+ /* We need to clear op_pending after we enqueue the mutex. */
+ __asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
/* Note that we deliberately exist here. If we fall
@@ -133,6 +141,8 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
int kind = PTHREAD_MUTEX_TYPE (mutex);
if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
{
+ /* We do not need to ensure ordering wrt another memory
+ access. Also see comments at ENQUEUE_MUTEX. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
NULL);
return EDEADLK;
@@ -140,6 +150,8 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
{
+ /* We do not need to ensure ordering wrt another memory
+ access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
NULL);
@@ -158,6 +170,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
id, 0);
if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
{
+ /* We haven't acquired the lock as it is already acquired by
+ another owner. We do not need to ensure ordering wrt another
+ memory access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return EBUSY;
@@ -171,13 +186,20 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
if (oldval == id)
lll_unlock (mutex->__data.__lock,
PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
+ /* FIXME This violates the mutex destruction requirements. See
+ __pthread_mutex_unlock_full. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return ENOTRECOVERABLE;
}
}
while ((oldval & FUTEX_OWNER_DIED) != 0);
+ /* We must not enqueue the mutex before we have acquired it.
+ Also see comments at ENQUEUE_MUTEX. */
+ __asm ("" ::: "memory");
ENQUEUE_MUTEX (mutex);
+ /* We need to clear op_pending after we enqueue the mutex. */
+ __asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
mutex->__data.__owner = id;
@@ -203,10 +225,15 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
if (robust)
- /* Note: robust PI futexes are signaled by setting bit 0. */
- THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
- (void *) (((uintptr_t) &mutex->__data.__list.__next)
- | 1));
+ {
+ /* Note: robust PI futexes are signaled by setting bit 0. */
+ THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
+ (void *) (((uintptr_t) &mutex->__data.__list.__next)
+ | 1));
+ /* We need to set op_pending before starting the operation. Also
+ see comments at ENQUEUE_MUTEX. */
+ __asm ("" ::: "memory");
+ }
oldval = mutex->__data.__lock;
@@ -215,12 +242,16 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
{
if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
{
+ /* We do not need to ensure ordering wrt another memory
+ access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return EDEADLK;
}
if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
{
+ /* We do not need to ensure ordering wrt another memory
+ access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
/* Just bump the counter. */
@@ -242,6 +273,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
{
if ((oldval & FUTEX_OWNER_DIED) == 0)
{
+ /* We haven't acquired the lock as it is already acquired by
+ another owner. We do not need to ensure ordering wrt another
+ memory access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return EBUSY;
@@ -262,6 +296,9 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
if (INTERNAL_SYSCALL_ERROR_P (e, __err)
&& INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
{
+ /* The kernel has not yet finished the mutex owner death.
+ We do not need to ensure ordering wrt another memory
+ access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return EBUSY;
@@ -279,7 +316,12 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
/* But it is inconsistent unless marked otherwise. */
mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
+ /* We must not enqueue the mutex before we have acquired it.
+ Also see comments at ENQUEUE_MUTEX. */
+ __asm ("" ::: "memory");
ENQUEUE_MUTEX (mutex);
+ /* We need to clear op_pending after we enqueue the mutex. */
+ __asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
/* Note that we deliberately exit here. If we fall
@@ -302,13 +344,20 @@ __pthread_mutex_trylock (pthread_mutex_t *mutex)
PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),
0, 0);
+ /* To the kernel, this will be visible after the kernel has
+ acquired the mutex in the syscall. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return ENOTRECOVERABLE;
}
if (robust)
{
+ /* We must not enqueue the mutex before we have acquired it.
+ Also see comments at ENQUEUE_MUTEX. */
+ __asm ("" ::: "memory");
ENQUEUE_MUTEX_PI (mutex);
+ /* We need to clear op_pending after we enqueue the mutex. */
+ __asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
}
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 6 ++++
nptl/pthread_mutex_trylock.c | 57 +++++++++++++++++++++++++++++++++++++++---
2 files changed, 59 insertions(+), 4 deletions(-)
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